C1-Symmetric Sulfoximines as Ligands in Copper-Catalyzed Asymmetric Mukaiyama-Type Aldol Reactions
Martin Langner and Carsten Bolm*
*Institut für Organische Chemie der Rheinisch-Westfälischen Technischen
Hochschule Aachen, Landoltweg 1, 52056 Aachen, Germany, Email: carsten.bolm
oc.rwth-aachen.de
M. Langner, C. Bolm, Angew. Chem. Int. Ed., 2004, 43, 5984-5987.
DOI: 10.1002/anie.200460953
Abstract
The synthesis of new C1-symmetric benzene-bridged aminosulfoximines is described. These aminosulfoximines are capable of serving as efficient ligands in copper-catalyzed enantioselective Mukaiyama-type aldol reactions.
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Details
The document details the use of C1-symmetric benzene-bridged aminosulfoximines as ligands in copper-catalyzed asymmetric Mukaiyama-type aldol reactions. Initially, C2-symmetric bissulfoximines and N-quinolyl-substituted sulfoximines yielded low enantioselectivities. However, novel C1-symmetric benzene-bridged benzylamino-sulfoximines demonstrated significant improvements. The reaction between 1-phenyl-1-(trimethylsilyloxy)ethene and methyl pyruvate, using copper(ii) triflate, served as a model. The best results were obtained with triisopropyl-substituted analogue 3e, achieving 93% enantioselectivity and over 99% yield. Further optimization, including solvent choice and reaction temperature, enhanced enantioselectivity to 98% ee. The study also explored the substrate scope, showing the catalyst's efficiency with various α-keto esters and enolsilyl ethers, achieving up to 99% ee. The research highlights the potential of these new ligands in enantioselective catalysis, comparing favorably with established systems like [Cu(tBubox)]2+ or [Sn(pybox)]2+. The document concludes with ongoing efforts to expand the substrate scope and apply the novel aminosulfoximines in other enantioselective catalyses. This work is supported by the Fonds der Chemischen Industrie and the Deutsche Forschungsgemeinschaft, emphasizing the significance of these findings in the field of asymmetric synthesis.
Key Words
aldol reaction, asymmetric catalysis, copper, N ligands, sulfoximines, Mukaiyama Aldol Addition, β-hydroxy carbonyl compounds
ID: J06-Y2004-860
